Eaton 912A587 Detroit Truetrac LSD Differential Ford 9 in. 28-Spline Ratio 3.25

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Product Specification:

SKU:EAT912A587

Weight: 16.9 lb

Inventory: 6

Type: Differentials

Vehicle Fitment

1957-1987 Ford Small Truck, Minivan, and SUV (Rear, Ford 9 in., All Models, Gear Ratio 3.25 & Up)
1957-1980 Ford, Lincoln, and Mercury Passenger Car (Rear, Ford 9 in., All Models, Gear Ratio 3.25 & Up)
1957-1972 Ford Half-Ton Truck, Van, and SUV (Rear, Ford 9 in., All Models, Gear Ratio 3.25 & Up)

Fitment Notes

Fits Ford 9 in. rear axle applications with 28-spline axle shafts and gear ratios of 3.25 and numerically higher only - not compatible with ratios below 3.25
Axle shaft diameter: 1.2 in. - confirm your axle shaft diameter before ordering
For use with standard carrier bore housing - reference Eaton's performance differential application guide to confirm fitment for your specific build before purchasing
Lubrication: Use petroleum/mineral-based GL-5 80W90 gear oil only - do NOT use synthetic gear oil or friction modifiers
Warranty is voided if used with tires exceeding 35 in. diameter

Features

Detroit Truetrac - the original helical gear limited slip differential introduced to the automotive aftermarket, and still the industry-leading clutchless LSD design
Patented parallel-axis planetary helix gear design automatically and proportionally biases torque toward the wheel with more traction the instant slip is detected
Clutchless, all-gear design means zero wearable parts - no clutch packs, no springs, no friction modifier required, and no scheduled maintenance ever
Operates smoothly and quietly like an open differential under normal driving; transitions seamlessly to traction-biasing mode when wheel slip is detected - fully automatic with no driver input required
No break-in procedure required - ready to perform from the first mile
Suitable for a wide range of applications: street and muscle, drag racing, circle track, restoration, work truck and towing, light trail and sand, rock crawl, and extreme off-road builds
At just 16.9 lbs, delivers maximum traction performance with minimal unsprung weight penalty
Engineered and manufactured by Eaton, a global drivetrain technology leader with over a century of vehicle performance innovation

Specifications

Part Number: 912A587
Differential Type: Limited Slip Differential (LSD) - Helical Gear / Detroit Truetrac
Axle Type: Ford 9 in.
Axle Location: Rear
Spline Count: 28
Axle Shaft Diameter: 1.2 in.
Compatible Gear Ratios: 3.25 & Up
Product Weight: 16.9 lbs
Recommended Fluid: Petroleum/Mineral-Based GL-5 80W90 Gear Oil
Synthetic Gear Oil: NOT Compatible
Friction Modifiers: NOT Required / NOT Compatible
Warranty: 1 Year from Date of Initial Retail Purchase

Included Components

1x Detroit Truetrac Helical Gear Limited Slip Differential Unit

Product Description

The Eaton 912A587 Detroit Truetrac is a helical gear limited slip differential built for the Ford 9 inch rear axle in 28-spline applications with gear ratios of 3.25 and up. Spanning a broad range of classic Ford, Lincoln, and Mercury vehicles from 1957 through the late 1980s - including passenger cars, trucks, vans, and SUVs - the 912A587 is one of the most widely used Truetrac units in restoration, muscle car, and vintage performance builds. The Truetrac's patented parallel-axis planetary helix gear design automatically biases torque to the wheel with more traction the moment slip is detected, without clutch packs, springs, or friction additives of any kind.

Operation is completely transparent to the driver: under normal conditions the unit feels and acts like an open differential, then seamlessly transfers torque bias when conditions demand it - no chatter, no clunk, no driver action required. With no wearable parts and no maintenance schedule, the 912A587 is a true fit-and-forget traction solution. At 16.9 lbs it adds minimal weight while delivering maximum reliability across street cruising, drag strip use, circle track, trail driving, and towing duty. Lubrication must be petroleum/mineral-based GL-5 80W90 gear oil - synthetic oils and friction modifiers are incompatible with the Truetrac helical gear design and will void the warranty.